1. Field of the Invention
The present invention relates to a digital video signal processing apparatus. More particularly, the present invention relates to an apparatus for detecting teletext information or video program system (VPS) information in a vertical blanking interval (VBI) in a color television broadcasting system such as a national television system committee (NTSC) system or a phase alternation by line (PAL) system and a method using the apparatus.
2. Description of the Related Art
FIG. 1 illustrates a waveform diagram of a frame of a video signal including a vertical blanking interval (VBI) signal. The frame of the video signal used in a national television system committee (NTSC) system or a phase alternation by line (PAL) system consists of two fields, i.e., an odd field and an even field. The frame has 625/PAL or 525/NTSC horizontal scan lines and a VBI between the two fields.
Teletext information or video program system (VPS) information may be included in the VBI signal. The teletext information is used to display text information in addition to an image on a screen. The VPS information is used to identify a TV program and for recording of the TV program at an airtime that is not a scheduled time.
FIG. 2 illustrates a waveform diagram of the VBI signal. Referring to FIG. 2, the teletext information or the VPS information is included in a plurality of VBI signals in several horizontal scan periods separated by a synchronization level and a color burst. The VBI signal may include a color burst, a clock run-in, a framing code and VBI data. The color burst is a quadrature amplitude modulated signal using a predetermined subcarrier frequency for determining a color component phase. The clock run-in is a 2-byte data signal identifying the existence of teletext information or VPS information. The framing code is a 1-byte data signal for providing a standard necessary for recognition of several teletext type (TTX) systems. VBI data used for transmission/reception of the VBI signal includes actual teletext information or VPS information.
A conventional apparatus for detecting teletext information uses a phase-locked loop (PLL). Thus, a high performance PLL is necessary for detecting teletext information. Thus, the manufacturing cost of the conventional apparatus is high.